Apparatus and method for monitoring the presence of volatile organic lead compounds

ABSTRACT

Apparatus and method for determining the presence of volatile organic lead compounds, such as alkyl lead, in an atmosphere, wherein the apparatus includes a tube of light-transmitting material having packed therein iodine crystals, means for driving an air stream through the tube and a photo-optical sensor adjacent the tube for sensing the presence of a predetermined amount of organic lead compound by detecting the color of a coating on the inner surface of the tube, and an alarm responsive to the triggering of the sensor.

O United States Patent 1 91 1111 3,870,469

Walker 1 Mar. 11 1975 i 1 APPARATUS AND METHOD FOR 2,787,782 4/1957 Roscnblum et a1. 340/237 R MONITORING THE PRESENCE 01: 3,114,610 12/1963 Gafford et a1 23/255 R 3,453,081 7/1969 Walker 23/232 R VOLAULE ORGANIC LEAD COMPOUNDS 3,694,087 9/1972 Lindberg 356/103 [75] Inventor: Alfred 0, Walker, Lake Jackson, 3,710,365 l/1973 Barnes 340/237 S Tex.

I Primary Examiner-Joseph Scovronek [73] Asslgnee' g Chemical Company Chlcdgo Attorney, Agent, or Firm-Lockwood, Dewey, Zickert & Alex [22] Filed: Apr. 30, 1973 [21] Appl. No.: 355,594 [57] ABSTRACT Apparatus and method for determining the presence [52] s CL n 23/232 E 23/255 E 250/574 of volatile organic lead compounds, such as alkyl lead, 340/237 356/103 in an atmosphere, wherein the apparatus includes a [51} ML CL G01 21/00, o 33/00 G081) 21/00 tube of light-transmitting material having packed [58] Field of Search n 23/232 R, 232 E 254 R, therein iodine crystals, means for driving an air stream 23/254 E 255 R, 255 E. 340/237 R 237 C through the tube and 8. photo-optical 5611801 adjacent 237 S. 250/5 4 573 574. 35 /103 th H1136 for sensing the presence Of a predetermined 3 amount of organic lead compound by detecting the [56] References Cited color of a coating on the inner surface of the tube, and

UNITED STATES PATENTS an alarm responsive to the triggering of the sensor. 2,561,802 7/1951 Klug 23/255 E 4 Claims, 3 Drawing Figures APPARATUS AND METHOD FOR MONITORING THE PRESENCE OF VOLATILE ORGANIC LEAD COMPOUNDS This invention relates in general to a method and apparatus for detecting the presence of volatile lead compounds in an atmosphere, and more particularly to a method and apparatus for continuously monitoring an atmosphere to determine the presence of volatile lead compounds and in the event that a predetermined amount of lead compounds is sensed to trigger an alarm means.

Heretofore it has been known to determine the presence of volatile organic lead compounds in an atmosphere by passing an air stream through a transparent tube packed with iodine crystals, wherein lead iodide coats the inner surface of the tube and can be visually detected because of the color of the coating, as is set forth in US. Pat. No. 3,453,081. However, such a method and apparatus has necessitated visual observation by an operator through constant inspection procedures.

The present invention obviates the above difficulties in providing an apparatus and method for continuously monitoring an atmosphere for the presence of volatile organic lead compounds, such as alkyl lead. More specifically, in addition to the presence of such a compound, the quantity is also monitored wherein an alarm is sounded when a predetermined quantity is detected.

In accordance with the invention, it has been found that the yellow coating of lead iodide on the inner surface of a transparent tube can be detected or sensed photo-optically wherein an alarm can be triggered upon such detection. As in the aforesaid patent, iodine crystals are packed in a tube made of transparent or light-transmitting material and an air stream effectively sampling the atmosphere to be monitored is driven through the tube and over the iodine crystals. In the event that the atmosphere is laden with a sufficient amount of volatile organic lead compound, such as an alkyl lead, a yellow coating is deposited on the inner surface of the tube in the area of the crystals, which is believed to be lead iodide. The yellow coating can be photo-optically detected by using a suitable light source and a suitable photocell arranged in spaced relation to the tube. By further connecting the photocell into an alarm circuit, an alarm may be triggered when the photocell detects a predetermined amount of yellow coating. Accordingly, the present invention avoids the necessity for periodic inspection of the tube as the alarm will be triggered in the event a sufficient amount of organic lead compound is detected in the atmosphere being monitored.

Accordingly, it is an object of the present invention to provide a new and improved apparatus and method for detecting the presence of volatile lead compounds in an atmosphere by continuously monitoring the atmosphere.

Another object of the present invention is in the provision of an apparatus and method for monitoring an atmosphere for the presence of volatile lead compounds, such as alkyl lead, by forcing an air stream taken from the atmosphere through a transparent tube packed with iodine crystals and photo-optically detecting the presence of lead iodide coating the interior of the tube adjacent the crystals.

Other objects, features and'advantages of the invention will be apparent from the following detailed disclosure, taken in conjunction with the accompanying sheet of drawings, wherein like reference numerals refer to like parts, in which:

FIG. 1 is a fragmentary perspective view with parts broken away of the apparatus according to the invention which detects the presence of volatile lead compounds in an atmosphere;

FIG. 2 is a somewhat diagrammatic but generally plan view of the apparatus according to FIG. 1; and

FIG. 3 is an electrical schematic diagram of the alarm circuit in which the photocell is arranged.

Referring now to the drawings, a tube 10 of lighttransmitting material is packed with a quantity of iodine crystals 1 1 held in place by a suitable porous material such as upper and lower glass wool plugs 12 and 13. In effect the tube is a sampling tube since an air stream is taken from the atmosphere to be monitored for the presence of volatile lead compounds and forced through the tube such as in the direction of the arrow 14 to thereby scrub the crystals with a sample of the atmosphere being monitored. The reaction of volatile lead compounds, such as alkyl lead, with the iodine crystals causes a yellow coating to be deposited on the inside surface of the tube in the form of lead iodide.

The present invention involves a method and apparatus of continuously monitoring any possible coating of lead iodide on the inner surface of the tube in the area of the crystals by photo-optically detecting the presence of the coating. More specifically, the photooptical sensor or detector includes a light source 15 and a photocell 16 both arranged adjacent to the tube and in the area of the iodine crystals. The light source 15 may be a neon or incandescent bulb or any other desired light source. A yellow filter 15a arranged between the light source and the tube assures that the light source is a yellow source of light so as to enhance the sensitivity of the photo-optical detector. In order to prevent direct illumination of the photocell from the light source, a light opaque shield 17 is arranged between the light source and the photocell. Moreover, the light source and the photocell are arranged at approximately apart relative to the axis of the tube and in a position to allow the photocell to receive scattered light from the yellow lead iodide coating and not receive any reflected light from the surface of thetube. Accordingly, the yellow coating serves to transmit or pipe the yellow light source to the photocell.

The coating of lead iodide on the inner surface of the tube 10 will be detected by the photocell 16, and when the light intensity reaches a predetermined level, an alarm circuit will be triggered. The photocell 16 is connected into a suitable alarm circuit to cause the energization of a suitable alarm such as a meter, a horn, a light or the like. Any suitable alarm or signal can be triggered when the photocell 16 is conditioned with detecting a sufficient light source depending upon the yellow coating of lead iodide on the inner surface of the tube. Exemplary of the type of alarm circuit'that could be used is the one shown in FIG. 3.

While the photo-optical system has been described as including a photocell 16, it should be appreciated that a photo-multiplier tube could be used in place of the photocell depending upon the sensitivity desired. The circuitry of FIG. 3 provides an on-off action whereby when the light energy on the photocell exceeds a predetermined level, the alarm will be turned on and otherwise the alarm will be off.

For convenience in describing the circuit, a plug is provided which permits the connection of the circuit to a suitable source of AC. or DC. power. Accordingly, power in the circuit enters through a fuse 21 and a main switch 22. Closing of the main switch applies power to the circuit. The photocell 16 is connected in series with a rectifying diode 23, a fixed resistor 24 and a variable resistor 25. Connected in parallel to the photocell 16 is a first transistor 26 where the emitter and collector are connected across the photocell. A resistor 27 is connected across the base and the emitter of the transistor while a second transistor 28 is connected across the first transistor 26 by connecting the collector of transistor 28 to the base of the transistor 26 and the base of the transistor 28 to the collector of the transistor 26. The variable resistor is connected between the emitter and base of transistor 28. A second diode 29 is connected in series with a fixed resistor 30 and a capacitor 31 as well as the resistor 24 and diode 23. A relay 32 is connected in parallel to the resistor and capacitor 31. The relay 32 includes an open contact 32a and a closed contact 3211 wherein when the relay is to be energized the relay arm 32c swings to the closed contact 32b to connect an alarm unit 34 to the potential provided through the plug 20.

In operation, when the light on the photocell 16 exceeds a predetermined level set by the variable resistor 25 and which also reduces the resistance of the photocell a predetermined amount as caused by the yellow coating on the inside of the tube, the circuitry will function to cause the relay 32 to fall out and to be deenergized, thereby connecting the alarm unit 34 to the electric potential warning an operator of the condition of the atmosphere being tested.

The following is representative of the components which may be utilized in the circuitry:

Resistor 24 5.6 ohms Resistor 25 250,000 ohms Resistor 27 150 ohms Resistor 30 470 ohms Capacitor 3| 5 microfarads Fuse 2! 3 am 5 Diode 23 SK 3 3l Diode 29 SK 3030 Transistor 26 SK 3005 Transistor 28 SK 3020 Photocell l6 Clairex 604 Relay 32 1.35 K, l2 volts As one example of setting up the circuit in FIG. 3, the variable resistor 25 will be adjusted so that the alarm will turn on when a change of 90,000 ohms (300,000 to 210,000) in the photocell 16 takes place responsive to the drawing through the tube of 500 to 1,000 micrograms of lead compounds.

From the foregoing it can be seen that the present invention is capable of automatically monitoring at all times the presence of lead compounds in an atmosphere and signaling to an operator in a remote location when a predetermined amount of lead compounds is detected.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention, but it is understood that this application is to be limited only by the scope of the appended claims.

The invention hereby claimed is:

1. Apparatus for continuously monitoring the presence of volatile organic lead compounds in an atmosphere and automatically producing a signal when a predetermined amount of lead compounds is detected therein which comprises, a tube of light transmitting material, iodine crystals in said tube, means causing the iodine crystals in said tube to be exposed to the atmosphere to be monitored by driving a stream of air from the atmosphere through the tube, a photo-optical sensor adjacent said tube sensing a predetermined color caused by lead iodide developing on the inner surface of the tube, said photo-optical sensor including a light source positioned adjacent the tube in the area of the crystals, a photocell positioned adjacent the tube in the area of the crystals and relative the tube axis about ninety degrees from the light source to receive scattered light from the lead iodide if it develops said predetermined color, and means preventing direct illumination of the photocell from the light source, and alarm means driven by said sensor and triggered when the crystals are subjected to a predetermined amount of lead compounds to cause said predetermined color to produce said signal.

2. Apparatus for continuously monitoring the presence of alkyl lead in an atomosphere and automatically producing a signal when a predetermined amount of lead compounds is detected therein, said apparatus comprising a tube of light-transmitting material, a quantity of iodine crystals packed in the tube, means continuously pumping a part of the atmosphere through the tube and crystals, a yellow light source adjacent the tube in the area of the crystals, a photocell adjacent the tube in the area of the crystals and displaced about from the light source, a light opaque shield between the light source and the photocell, and an alarm system connected to the photocell and triggerable when a predetermined amount of lead iodine developes on the inner surface of the tube in the area of the crystals to produce said signal.

3. A method of continuously monitoring the presence of volatile lead compounds in an atmosphere and automatically producing a signal when a predetermined amount of lead compounds is detected therein which comprises the steps of, continuously subjecting iodine crystals in a tube of light-transmitting material to a stream of air taken from the atmosphere, photooptically detecting the color of a coating of lead iodide developing on the inner surface of the tube including positioning a light source adjacent the tube in the area of the crystals, positioning a photocell adjacent the tube in the area of the crystals and spaced about ninety degrees therefrom relative the axis of the tube, and positioning a light opaque shield between the light source and photocell, and triggering an alarm to produce said signal when the coating turns a predetermined color indicating a predetermined quantity of lead compounds in the atmosphere.

4. The method of claim 3, wherein the step of detecting further includes positioning a yellow filter in front of the light source. 

1. APPARATUS FOR CONTINUOUSLY MONITORING THE PRESENCE OF VOLATILE ORGANIC LEAD COMPOUNDS IN AN ATMOSPHERE AND AUTOMATICALLY PRODUCING A SIGNAL WHEN A PREDETERMINED AMOUNT OF LEAD COMPOUNDS IS DETECTED THEREIN WHICH COMPRISES, A TUBE OF LIGHT TRANSMITTING MATERIAL, IODINE CRYSTALS IN SAID TUBE, MEANS CAUSING THE IODINE CRYSTALS IN SAID TUBE TO BE EXPOSED TO THE ATMOSPHERE TO BE MONITORED BY DRIVING A STREAM OF AIR FROM THE ATMOSPHERE THROUGH THE TUBE, A PHOTO-OPTICAL SENSOR ADJACENT SAID TUBE SENSING A PREDETERMINED COLOR CAUSED BY LEAD IODIDE DEVELOPING ON THE INNER SURFACE OF THE TUBE, SAID PHOTO-OPTICAL SENSOR INCLUDING A LIGHT SOURCE POSITIONED ADJACENT THE TUBE IN THE AREA OF THE CRYSTALS, A PHOTOCELL POSITIONED ADJECENT THE TUBE IN THE AREA OF THE CRYSTALS AND RELATIVE THE TUBE AXIS ABOUT NINETY DEGREES FROM THE LIGHT SOURCE TO RECEIVE SCATTERED LIGHT FROM THE LEAD IODIDE IF IT DEVELOPS SAID PREDETERMINED COLOR, AND MEANS PREVENTING DIRECT ILLUMINATION OF THE PHOTOCELL FROM THE LIGHT SOURCE, AND ALARM MEANS DRIVEN BY SAID SENSOR AND TRIGGERED WHEN THE CRYSTALS ARE SUBJECTED TO A PREDETERMINED AMOUNT OF LEAD COMPOUNDS TO CAUSE SAID PREDERMINED COLOR TO PRODUCE SAID SIGNAL.
 1. Apparatus for continuously monitoring the presence of volatile organic lead compounds in an atmosphere and automatically producing a signal when a predetermined amount of lead compounds is detected therein which comprises, a tube of light transmitting material, iodine crystals in said tube, means causing the iodine crystals in said tube to be exposed to the atmosphere to be monitored by driving a stream of air from the atmosphere through the tube, a photo-optical sensor adjacent said tube sensing a predetermined color caused by lead iodide developing on the inner surface of the tube, said photo-optical sensor including a light source positioned adjacent the tube in the area of the crystals, a photOcell positioned adjacent the tube in the area of the crystals and relative the tube axis about ninety degrees from the light source to receive scattered light from the lead iodide if it develops said predetermined color, and means preventing direct illumination of the photocell from the light source, and alarm means driven by said sensor and triggered when the crystals are subjected to a predetermined amount of lead compounds to cause said predetermined color to produce said signal.
 2. Apparatus for continuously monitoring the presence of alkyl lead in an atmosphere and automatically producing a signal when a predetermined amount of lead compounds is detected therein, said apparatus comprising a tube of light-transmitting material, a quantity of iodine crystals packed in the tube, means continuously pumping a part of the atmosphere through the tube and crystals, a yellow light source adjacent the tube in the area of the crystals, a photocell adjacent the tube in the area of the crystals and displaced about 90* from the light source, a light opaque shield between the light source and the photocell, and an alarm system connected to the photocell and triggerable when a predetermined amount of lead iodide develops on the inner surface of the tube in the area of the crystals to produce said signal.
 3. A method of continuously monitoring the presence of volatile lead compounds in an atmosphere and automatically producing a signal when a predetermined amount of lead compounds is detected therein which comprises the steps of, continuously subjecting iodine crystals in a tube of light-transmitting material to a stream of air taken from the atmosphere, photo-optically detecting the color of a coating of lead iodide developing on the inner surface of the tube including positioning a light source adjacent the tube in the area of the crystals, positioning a photocell adjacent the tube in the area of the crystals and spaced about ninety degrees therefrom relative the axis of the tube, and positioning a light opaque shield between the light source and photocell, and triggering an alarm to produce said signal when the coating turns a predetermined color indicating a predetermined quantity of lead compounds in the atmosphere. 